Recent work has established that, contrary to being uncommon, childhood-onset bipolar disorder (BD) may account for a significant number of child psychiatry referrals (Faedda et al., 1995; Geller and Luby, 1997; Weller et al., 1995; Weller et al., 1986). Studies indicate that up to 16% of youth in child psychiatry clinics may have BD (Wozniak et al., 1995). Moreover, children with major depression are at high risk to develop BD (Geller et al., 1994; Strober and Carlson, 1982). Bipolar disorder in children and adolescents is often familial (Chang et al., 2000; Strober, 1992; Strober et al., 1988). Current limited data suggest children with BD have a chronic course of the illness, characterized by continued morbidity, comorbidity and mood cyclicity (Geller et al., 2001; Geller et al., 2002).

Presentation

By adult standards, children with BD present with an atypical clinical picture, with irritability, mixed presentation and chronicity (Ballenger et al., 1982; Weller et al., 1995; Wozniak et al., 2001). While severe irritability can be a common characteristic in children with or without a psychiatric diagnosis, the irritability associated with mania has a much more hostile, vicious and attacking quality (Davis, 1979). In addition to a general level of irritability, children with mania also present with extremely impairing dysphoric, explosive episodes that generally occur daily with little or no precipitant. These explosions can last up to an hour or longer and may involve destruction of property such as kicking holes in walls and throwing and breaking household items. During these rages, children are hard to calm and often lash out physically at those around them. Swearing and hostile comments are also common. Parents almost universally say they "walk on eggshells" out of fear of these unpredictable outbursts (Wozniak et al., 2001).

Descriptions of euphoric moods are generally elicited by inquiring for giddy, goofy, hyperexcited, silly states with laughing fits. Parents often describe the child acting in an immature, clownish manner to the extent of alienating others. Grandiosity or flight of ideas can occur in the euphoric or irritable states. Parents also describe their children as having an extreme degree of grandiose defiance, refusing to comply with authority at home or at school. Children with BD often have comorbid oppositional defiant disorder (Wozniak et al., 2001). The defiant state has a grandiose quality that generates problems at home, in school, and in sports or other activities. Children will believe themselves to "know better" than adults around them and on this basis refuse to comply with what they see as petty or "stupid" demands put on them. These children are often labeled as having "an attitude problem" and inspire the anger of adults.

Little is known about the variations between mania and depression in children and adolescents with BD. In our sample of children meeting criteria for mania, 86% have also had a depressive episode, and 90% have had the depressive episode overlap in time with the manic episode, representing a mixed state (Wozniak et al., 1995; Wozniak et al., 1993). This is usually described as children unpredictably switching in and out of depression, irritable mania with explosions and euphoric mania throughout the day, almost every day, with very little time spent in a regular age-appropriate mood state. Such a state has been referred to as ultradian rapid cycling (Geller et al., 1995) and has been noted by a number of investigators (Findling and Calabrese, 2000; Wozniak et al., 1995). Because of the switching among these mood states, it is very difficult for some parents to agree that the child has had a full week of irritability or a full week of euphoria as required by some clinicians. On the other hand, parents describe periods of a mix of abnormal mood states spanning years with little normalcy. A better characterization, then, would be abnormal moods present almost every day, most of the days, for a majority of the time.

Bipolar disorder generally has an insidious onset in children. In our sample, nearly one-quarter of parents could not identify an age of onset, but felt that the child had "always" had an abnormal mood, even by infant standards (Wozniak et al., 1995). Of the children with the abnormal mood states noted above, the average age of onset of the manic syndrome was 4.4 years with 70% described as beginning under age 5.

Preschoolers with BD share many clinical characteristics of BD with their older counterparts. We recently described the clinical characteristics and functioning of 44 preschoolers (4 to 6 years of age) with BD and compared them to 29 school-aged children (7 to 9 years) with BD (Wilens et al., 2002). We found that preschoolers had similar rates of comorbid psychopathology of attention-deficit/hyperactivity disorder, disruptive disorders and anxiety disorders compared to school-aged youth. Preschoolers and school-aged children with BD typically manifest symptoms of mania and depression simultaneously (mixed states). Both preschoolers and school-aged children had substantial impairment in (pre)school, social and overall functioning.